1,549 research outputs found
Detection of Rotational Spectral Variation on the M-type asteroid (16) Psyche
The asteroid (16) Psyche is of scientific interest because it contains ~ 1%
of the total mass of the asteroid belt and is thought to be the remnant
metallic core of a protoplanet. Radar observations have indicated the
significant presence of metal on the surface with a small percentage of
silicates. Prior ground-based observations showed rotational variations in the
near-infrared (NIR) spectra and radar albedo of this asteroid. However, no
comprehensive study that combines multi-wavelength data has been conducted so
far. Here we present rotationally resolved NIR spectra (0.7-2.5 microns) of
(16) Psyche obtained with the NASA Infrared Telescope Facility. These data have
been combined with shape models of the asteroid for each rotation phase.
Spectral band parameters extracted from the NIR spectra show that the pyroxene
band center varies from ~ 0.92 to 0.94 microns. Band center values were used to
calculate the pyroxene chemistry of the asteroid, whose average value was found
to be Fs30En65Wo5. Variations in the band depth were also observed, with values
ranging from 1.0 to 1.5%. Using a new laboratory spectral calibration we
estimated an average orthopyroxene content of 6+/-1%. The mass-deficit region
of Psyche, which exhibits the highest radar albedo, also shows the highest
value for spectral slope and the minimum band depth. The spectral
characteristics of Psyche suggest that its parent body did not have the typical
structure expected for a differentiated body or that the sequence of events
that led to its current state was more complex than previously thought.Comment: 21 pages, 8 figures, 2 tables, published in The Astronomical Journa
Reconciliation through Description: Using Metadata to Realize the Vision of the National Research Centre for Truth and Reconciliation
PostprintThis articlewill discuss the history and context surrounding the document collection and statement gathering mandates of the Truth and Reconciliation Commission of Canada and the challenges the newly established National Research Centre for Truth and Reconciliation will face in applying the Commission’s metadata set in the realization of its vision. By working respectfully with Indigenous people through the implementation of Indigenous knowledge best practices and the application of contrasting traditional/nontraditional, archival/user-generated, and institutional/Indigenous descriptive elements, the Centre will attempt to create a “living archive” and facilitate Indigenous participation, collaboration, and ultimately, the process of reconciliation.https://www-tandfonline-com.uwinnipeg.idm.oclc.org/doi/full/10.1080/01639374.2015.100871
Growth rate of binary words avoiding
Consider the set of those binary words with no non-empty factors of the form
. Du, Mousavi, Schaeffer, and Shallit asked whether this set of words
grows polynomially or exponentially with length. In this paper, we demonstrate
the existence of upper and lower bounds on the number of such words of length
, where each of these bounds is asymptotically equivalent to a (different)
function of the form , where , are constants
A new polymorph of phenylselenium trichloride
A second polymorph of phenylselenium trichloride, PhSeCl3 or C6H5Cl3Se, is
disclosed, which is comprised of asymmetric chlorine-bridged noncovalent
dimer units rather than polymeric chains. These dimers are each weakly bound
to an adjacent dimer through noncovalent Se...Cl bonding interactions. Phenyl
rings within each dimer are oriented in a syn fashion. Density functional theory
(DFT) calculations reveal that the putative anti isomer is within 5 kJ mol-1 of
the experimentally observed form. This structure represents the first additional
polymorph discovered for an organoselenium trihalide compound.https://doi.org/10.1107/S205322961901301
Building the System: Follow-up, monitoring & adaptive management
Does impact assessment (IA) end when the license has been granted? While societal resources tend to focus on rigorous project approvals, what happens to the project, to the public and to the environment once approval is granted? Follow up and monitoring are often an afterthought for legislators, public servants and proponents. But they are critical to public confidence and to ensuring that proponents live up to their commitments in a rapidly changing world."This report draws from research funded by the Impact Assessment Agency as part of the Social Sciences and Humanities Research Council of Canada Knowledge Mobilization Grant on Informing Best Practice in Environmental and Impact Assessment.
A family of formulas with reversal of high avoidability index
We present an infinite family of formulas with reversal whose avoidability index is bounded between 4 and 5, and we show that several members of the family have avoidability index 5. This family is particularly interesting due to its size and the simple structure of its members. For each k ∈ {4,5}, there are several previously known avoidable formulas (without reversal) of avoidability index k, but they are small in number and they all have rather complex structure.http://dx.doi.org/10.1142/S021819671750024
The metric dimension and metric independence of a graph
A vertex x of a graph G resolves two vertices u and v of G if the
distance from x to u does not equal the distance from x to v. A set
S of vertices of G is a resolving set for G if every two distinct vertices
of G are resolved by some vertex of S. The minimum cardinality of a
resolving set for G is called the metric dimension of G. The problem of
nding the metric dimension of a graph is formulated as an integer pro-
gramming problem. It is shown how a relaxation of this problem leads
to a linear programming problem and hence to a fractional version of
the metric dimension of a graph. The linear programming dual of this
problem is considered and the solution to the corresponding integer
programming problem is called the metric independence of the graph.
It is shown that the problem of deciding whether, for a given graph
G, the metric dimension of G equals its metric independence is NP-
complete. Trees with equal metric dimension and metric independence
are characterized. The metric independence number is established for
various classes of graphs.Preprin
On the Andrews congruence for the Fibonacci quotient
We show that a congruence discovered by George E. Andrews in 1969 for the
Fibonacci quotient directly implies a simpler congruence found by Hugh C.
Williams in 1991
Binary words avoiding xx^Rx and strongly unimodal sequences
In previous work, Currie and Rampersad showed that the growth of the number
of binary words avoiding the pattern xxx^R was intermediate between polynomial
and exponential. We now show that the same holds for the growth of the number
of binary words avoiding the pattern xx^Rx. Curiously, the analysis for xx^Rx
is much simpler than that for xxx^R. We derive our results by giving a
bijection between the set of binary words avoiding xx^Rx and a class of
sequences closely related to the class of "strongly unimodal sequences."Comment: 4 page
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